title: Effects of resting vagal tone on accessory atrioventricular connections.
abstract: The purpose of this study was to determine the effects of resting vagal tone on accessory atrioventricular (AV) connections. Atropine (0.04 mg/kg) was administered to 13 patients with the Wolff-Parkinson-White syndrome and was found to have the following effects on the accessory AV connection: the anterograde block cycle length shortened from 305 +/- 51 to 279 +/- 54 msec (mean +/- SD; p less than 0.001); the retrograde block cycle length shortened from 288 +/- 57 to 251 +/- 50 msec (p less than 0.001); and the effective refractory period measured at a basic drive cycle length of 400 msec shortened from 295 +/- 45 to 265 +/- 47 msec in the anterograde direction (p less than 0.001) and from 283 +/- 18 to 261 +/- 12 msec in the retrograde direction (p less than 0.01). During atrial fibrillation, the mean ventricular cycle length decreased from 434 +/- 88 to 352 +/- 56 msec (p less than 0.001), and the shortest preexcited RR interval decreased from 302 +/- 56 to 256 +/- 43 msec (p less than 0.01). In another seven patients, propranolol (0.2 mg/kg) was administered before atropine, and atropine lengthened the anterograde block cycle length and the effective refractory period of the accessory AV connection; the magnitude of these effects was similar to that in the patients who did not receive propranolol. In conclusion, these data demonstrate that resting vagal tone exerts a direct depressant effect on accessory AV connections that does not require background sympathetic activity to be manifest.
authors.affiliation: Division of Cardiology, University of Michigan Medical Center, Ann Arbor, MI 48109.
authors.forename: F
authors.initials: F
authors.lastname: Morady
authors.forename: A H
authors.initials: AH
authors.lastname: Kadish
authors.forename: S
authors.initials: S
authors.lastname: Schmaltz
authors.forename: S
authors.initials: S
authors.lastname: Rosenheck
authors.forename: J
authors.initials: J
authors.lastname: Summitt
mesh_terms: D000328:Adult; D001283:Atrioventricular Node / Q000187:drug effects / Q000503:physiopathology*; D001285:Atropine / Q000494:pharmacology; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D009434:Neural Pathways / Q000187:drug effects / Q000503:physiopathology; D011433:Propranolol / Q000494:pharmacology; D012032:Refractory Period, Electrophysiological / Q000187:drug effects; D014630:Vagus Nerve / Q000503:physiopathology*; D014927:Wolff-Parkinson-White Syndrome / Q000503:physiopathology
chemical_list: D001285:Atropine; D011433:Propranolol